In nuclear facilities, particularly plants for reprocessing irradiated nuclear fuels, the discharge of non-radioactive liquids such as sanitary waste from the radioactive controlled areas must be monitored so that the appropriate action can be taken should these substances prove to carry an undesired radioactive charge. The non-radioactive liquids and sanitary waste originate in non-radioactive areas within the controlled area, for example, in sanitary blocks.
Since every effort is made to minimize radioactive waste from controlled areas, it is necessary that the non-radioactive liquids be safely passed into the drainage system as a non-radioactive substance. This applies especially to sanitary waste which constitutes a very large volume together with the flushing water used in expanded controlled areas.
In nuclear medicine, it is normal practice for the toilets in a toilet layout to be connected to a decay container. Mounted on this decay container is a detection device by means of which the decay of short-lived radioisotopes can be monitored. After decay to below a specific level of radioactivity, the water can be passed into the drainage system.
This solution to the problem is only suitable for nuclear medical departments of hospitals in which short-lived radioisotopes are used for therapeutic or diagnostic purposes.
Published German patent application 2,851,781 discloses a decay plant for radioactively charged fecal waste from toilet systems in which all the toilets are connected to a measuring container. The measuring container has a station at which the radioactivity is measured. The result of the measurement actuates shutoff means which control dispersal into two different decay containers.
This apparatus is used for toilet systems by means of which it is intended to effect a controlled discharge of radionuclides administered during therapy and diagnosis. In the case of radionuclides with a long half-life value such as may well be present in other nuclear facilities, the entire apparatus would be contaminated so that any newly introduced non-radioactive liquid would again be contaminated.